Multinuclear magnetic resonance study of the complexation of lanthanum (III) by d-glucitol and ribitol in aqueous solution

A multinuclear magnetic resonance study (1H, 13C, 139La) of the interactions of La(III) with d-glucitol and ribitol in aqueous solution is presented and is compared with recently published calorimetric data. The thermodynamic data were determined by 139La NMR, and are in excellent agreement with the calorimetric results: ΔH° = − 10.3 ± 1.2 kJ mol−1 and ΔS° = − 25.7 ± 3.9 J K−1 mol−1 (139La NMR); ΔH° = − 10.2 kJ mol−1 and ΔS° = − 25.8 J K−1 mol−1 (calorimetry; from Rongère et al., op. cit.). A conformational analysis of d-glucitol shows that the complexation of La(III) results from a 120° rotation of the C2-C3 bond in the most stable conformation of d-glucitol, thus providing three hydroxyl groups in a suitable spatial arrangement for the occupancy of the first coordination sphere of La(III) and the concurrent replacement of water molecules. © 1997 Elsevier Science Ltd.